Method and apparatus for treating materials

ABSTRACT

A METHOD AND APPARATUS IS DISCLOSED FOR FORMING MATERIALS INTO DESIRED SHAPES BY ROLLING OR CASTING. THE ROLLED SHAPES MAY BE OF CONSTANT OR IRREGULAR CROSS SECTION. THE APPARATUS INCLUDES LATERAL RESTRAINT MEMBERS THAT MOVE   WITH THE WORKPIECE TO PREVENT EDGE CRACKING IN ROLLING OR PROVIDE A MOVING WALL DIE IN CASTING.

Feb. 9, 1971 J,A SHEY 3,561,240

METHOD AND APPARATUS FOR TREATING MATERIALS Filed Dec 7, 1967 r sSheets-Sheet 1 /A/VE/VTOR. JOH/VA .SCHE) Feb; 9,1911 I A, g HEY3,561,240

METHOD AND AFPARATUS FOR TREATING MATERIALS Filed Dec. 7, 1967 v 3Sheets-Sheet 5 M IVEIVTOR JOHN A. SCHEY United States Patent US. Cl.72-184 9 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus isdisclosed for forming materials into desired shapes by rolling orcasting. The rolled shapes may be of constant or irregular crosssection. The apparatus includes lateral restraint members that move withthe workpiece to prevent edge cracking in rolling or provide a movingWall die in casting.

This application is a continuation-in-part of my copending applicationSer. No. 587,358, filed Sept. 16, 1966, which application is acontinuation-in-part of my application Ser. No. 444,637, filed Apr. 1,1965, and now abandoned.

The present invention relates to a novel process and apparatus usefultherewith for the rolling or casting of various materials and moreparticularly is directed to a relatively simple means of preventing edgecracking in the rolling aspect hereof. While my invention may be usedwith a number of materials which are subject to edge cracking uponrolling it has special applicability for the treatment of metals andfurthermore my invention is useful in the continuous casting of metalingots.

My invention is useful not onl in the rolling and casting of materialssuch as metal sheets, slabs and plates, but also may readily be employedin the consolidation of metal powders into an integral body.

The essential feature of the rolling aspect of my invention involvesrolling under complete lateral restraint with the lateral restrainingmembers moving with the rolls and by employing such restraint I havediscovered that I can readily and conveniently roll without producingedge cracking in those materials which hithertofore, to the best of myknowledge, have never been rolled without edge cracking. The utility andimportance of such discovery will be immediately apparent to thoseskilled in this particular art.

Another aspect of this invention is directed to the continuous castingof molten metal or the like into solid ingots by use of only slightlymodified apparatus from that which is used in the edge restraint rollingembodiment hereof. As is well known to those skilled in this art moldswhich have previously been used in the continuous casting of materials,particularly metals, are usually made in the form of a cooled framewhich is oscillated and/or critically lubricated to provide the meansfor separating the cast ingot from the mold. In some prior art processesthe mold moves; in others water cooled drums or rolls are used to castthin bands; another process employs a grooved wheel with a cover bandfor casting wire bars.

All of such prior art continuous casting processes suffer a number ofdisadvantages. Internal porosity and surface defects are common in allof the resulting cast materials except those made with the water cooleddrums and the latter process yields materials of limited thickness dueprimarily to the failure to enclose the roll gap from the sides.

In distinction to these problems encountered in prior 3,561,240 PatentedFeb. 9, 1971 art continuous casting methods, the present processprovides excellent continuously cast ingots without any severe sizelimitations. All of this will be set out in greater detail as thedescription proceeds.

Accordingly, a primary object of my invention is to provide a method ofpreventing edge cracking during the rolling of metal structures whichprocess includes as its most important step edge restraint at the sidesof the material being rolled and which edge restraint members aremovable with the rolling mechanisms.

Another object of my invention is to provide a material rolling processwhereby edge cracking is markedly reduced or eliminated.

Still a further object of my invention is to provide a method andapparatus for the rolling of nonuniform cross sections under lateralrestraint.

Another object of my invention is to provide apparatus for use in thepresent process.

These and other objects, features and advantages of my invention willbecome apparent to those skilled in this particular art from thefollowing detailed disclosure thereof and the accompanying drawings inwhich:

FIG. 1 schematically illustrates a roll element for use in the presentprocess;

FIG. 2 is a view taken along lines 22 of FIG. 1 in partial section andalso schematically illustrates the practice of the present process andthe equipment required herewith;

FIG. 3 schematically illustrates another embodiment of the process andapparatus of the present invention; and

FIG. 4 schematically illustrates still another embodiment hereofespecially useful in the rolling of powder materials; and

FIG. 5 illustrates another embodiment of the present invention inpartial cross section as in FIG. 2; and

FIG. 6 shows a product produced by the apparatus of FIG. 5; and

FIG. 7 is an enlarged cross section taken along line 77 of FIG. 6.

Before considering the present invention, reference should first bebriefly had to the edge cracking problems encountered in the rolling ofmetal bodes as taught by the practices of the art prior to my invention.Obviously the rolling of fiat slabs or sheets of metal has been carriedout for a long time. Present industrial practices are a culmination ofalmost a century of effort and development in metal rolling and metalrolling techniques, but to the best of my knowledge until the presentinvention was made one of the most vexing problems faced by thoseoperating in this area of technology, namely edge cracking, had notreally been solved. Eiforts directed to the elimination of edge crackinghave been made but I know of no comparable process which eithercompletely eliminates edge cracking or so markedly reduces suchphenomena as results from the practice of edge restraint rolling as istaught in the present specification.

Others have attempted to alleviate this problem by, for example, rollingin grooved rolls or by the employment of vertical edge rollers. Neitherof these processes have brought about any degree of improvement akin tomy findings in the process herein described. As a result, edge crackingin crack-sensitive materials remains a serious problem and scrap lossesdue to edge cracking account for a substantial portion of the presentproduction costs of some of the newer so-called exotic materials. Infact many materials with desirable mechanical properties have had to besomewhat abandoned because of their uncontrollable edge cracking or inthe alternative, had to be produced by expensive methods in order tobreak down their cast structure. A similar situation has existed in thecompaction of metal powders.

While the term edge cracking" is self explanatory I merely wish to sayat this point that it alludes to the cracking, splitting, breaking of ametal structure during rolling at the uncovered lateral sides thereof.As used in the present specification and claims the term also refers tosimilar detrimental phenomena occurring in materials other than metals.It appears that edge cracking is caused by secondary tensile stresseswhich are inevitable whenever metal or other material spread occurs asin rolling. The result has been with many materials that either they cannot be rolled at all or there was a considerable loss involved intrimming the cracked portions off of the central body of the rolledmaterial. The economic loss has been significant.

It has been perhaps recognized that edge cracking can be prevented onlyby the complete elimination of spread in the roll gap but prior to mypresent invention no workable solutions for this problem existed. Themost widely practiced partial remedy is rolling in closed passes. Suchpasses are closed by interlocking annular projections (i.e., shouldersor the like) of the rolls. Such solution suffers from severallimitations: The slab may be entered into the closed pass only at asubstantially narrower width for otherwise the spreading material willfirmly wedge between the shoulders of the roll and instead of beingreleased at the exit side it will be wound around the roll. It istherefore common practice to allow almost free spread in the closed passwith consequent edge cracking of sensitive materials. In the rolling ofpowders the problem may be somewhat alleviated by placing one shoulderon each of the opposite rolls as disclosed in the patent to Naeser, US.3,019,487, and Dasher et al., US. Pat. 3,017,665, thereby imparting atwist on the exiting strip product and freeing it from the confines ofthe roll gap. Such solution, however, is obviously unworkable with solidmaterial having full density especially when such material has asubstantial thickness. Furthermore, a three dimensional consideration ofthe problem will show that edge restraint in closed passes can beprovided only if the shoulders of the rolls are big enough to cover theentire zone of deformation; the requisite large shoulders produce asubstantial annular velocity difference between the rolled material andvarious parts of the closed pass with a resulting undesirable distortionand wear. Furthermore, it is impossible to reintroduce the materialrolled in a closed pass into the same pass for further reduction and theheavy total reduction normally sought for can be achieved only in asuccession of closed passes which for the reasons noted above must besuccessively widened thus opening the way for further edge cracking.

The edge cracking problems in rolling are substantially completelyeliminated by the practice of my invention. By complete edge restraintlaterally at right angles to the material being rolled edge cracking issubstantially or completely eliminated in the rolling of most metals andother materials subject to edge cracking. It is important in thepractice of such edge restraint that the lateral restraining members bemovable with the rolls and with the material being rolled.

To understand my invention reference should next be had to FIGS. 1 and 2hereof. Here is illustrated a twohigh rolling mill having a top roll 11and a bottom roll 12. A metal slab 13 being rolled is interposed betweenthe rolls in the usual manner. Grooves 14 are provided in the rolls,said grooves being in register for both the top and bottom roll and asshown in the drawing, are lateral to the central part of the roll. Inthe two lateral grooves I insert a pair of restraining bars 16. It issuch restraining bars 16 in this embodiment of my invention whichprovide the edge restraint of the material being rolled. The restrainingbars are made of various strong materials, e.g., alloys similar to thoseof which the rolls are fabricated; therefore, as in the case of therolls, they are relatively incompressible compared to the material beingrolled.

As clearly shown in FIG. 1 the rolled slab 13 is now rolled in a tightlyclosed, i.e., vertically and horizontally closed, chamber which not onlyprovides the usual rolling but also tight and strong edge restraint.

Parenthetically, while a solid metal slab is illustrated in FIGS. 1 and2 it will of course be apparent that metal powders may be substitutedtherefor and compacted and consolidated in the present process. Variousother materials subject to edge cracking upon rolling may be similarlytreated.

The restraining bars 16 closely but movably fit in the grooves 14 of theupper and lower rollers and thus their movement laterally is restrained.As shown in FIG. 1 each such restraining bar rests in the bottom of thegroove provided in the lower roll and there is a space 15 left forclearance purposes between the top of the restraining bar and the top ofthe groove of the top roll 11. But because of such grooving therestraining bars 16 are held in close restraint to prevent lateralmovement. The clearance 15 permits repeated thickness reductions of theslab being rolled by closing the rolls in the usual manner.

As shown in FIG. 2 the restraining bars are positioned on table rollers17 and are assisted in being maintained in operative position by guiderollers 18.

It will be apparent that the grooved rolls permit the closing of therolls and thus its operation is substantially as flexible as that with aconventional two-high rolling mill, except of course the width of therolled slab now remains constant. By such configuration I obtain themarked reduction in edge cracking previously alluded to. The restrainingelements prevent side spread and rolling is carried out under planestrain conditions. Thus the development of harmful secondary tensilestresses is entirely suppressed.

By employing edge restraint through elements that do not form part ofthe rolls my invention solves all of the earlier mentioned problemsassociated with the elimination of edge cracking. The material islaterally supported in the entire zone of deformation. Velocitydifferences between the rolled material and the restraining elements arereduced to a minimum and the material may be reentered into the samepair of rolls for succession of passes with zero spread. The rolledproduct is readily removed from the roll gap without twisting orscraping.

A number of materials were rolled with edge restraint as herein taughtto clearly point up the edge cracking prevention resulting from myprocess. For example:

Aluminum alloy slabs containing 8% magnesium were prepared and subjectedto rolling both with and without edge restraint as herein taught. Allslabs of this material rolled without such restraint invariably crackedat the edges whereas the restrained ones gave perfect parallel edgesabsolutely free of cracking.

Powder bodies of iron powders were made by ramming them into shape andthen rolling at 2400 F. both with and without edge restraint as hereintaught. The nonrestrained bodies cracked severely; their density wasapproximately 70% of theoretical density of iron after 70% to reductionin thickness. Similar powder bodies rolled with edge restraint as hereintaught gave dense bodies free of edge cracks and with mechanicalproperties similar to those of typical hot rolled slabs. In thisparticular aspect of my invention an appropriate protective atmosphereshould be employed.

Metal powder bodies were made by ramming them into a mild steel sheath.When rolling without edge restraint the sheath broke open and much ofthe powder escaped. By using the restraining bars the rolled body wasfree of edge cracking and yielded a much superior compacted product witha density approaching theoretical after only 70% reduction in thickness.

In the foregoing embodiment of my invention the process and apparatus isprimarily suited for operation in reversing mills where a succession ofpasses may be taken on one and the same slab without need of separatingthe slab from the restraining elements. In anotherembodiment hereof asillustrated in FIG. 3 the restraining elements are in the form ofendless belts 21. Here such belts fit into lateral grooves 22 on therolls. While the thickness of such belts is of necessity limited by therequirement to maintain their flexibility adequate strength can beobtained for edge restraint purposes in view of the support that suchbelts receive from the portion of the rolls which firm the outer wall ofthe grooves 22. The clearance between belts 21 and grooves 22 is greatlyexaggerated in the schematic illustration of FIG. 3.

The present process and apparatus can also be employed for cladding. Forthis purpose a cladding material may be fed through the input side ofthe roll pair onto the base metal or other material being rolled withedge restraint.

The present process may also be employed in the rolling of materialsother than metals. For example ceramics which are sheathed or canned ina metal may be rolled with edge restraint to prevent edge cracking ofthe composite structure.

It should also be evident to those skilled in this particular art thatthe present process may be employed in the rolling of complex shapesrather than mere plates or sheets as hereinabove described. As is moreclearly described hereinafter With reference to FIG. 5 my process willlikewise prevent edge cracking in such shapes which hithertofore weresubject to such detrimental phenomena.

In the compaction and rolling of loose particulate matter as hereintaught, a variety of known means can be employed to bring such matterinto position in the roll gap. I prefer, however, that a pair ofconverging belts be used to convey, for example, powders into the gap.This is illustrated schematically in FIG. 4. Here again there is anupper and lower roll 11 and 12 respectively and edge restraint isprovided by belts or rings 23. To bring the powders in, endless belts 24and 25 are mounted on rollers and positioned as shown. The belts 24 and25 together with the restraining elements 23 define a feeding throatwhich tapers into the roll gap. By virtue of the movement of all foursides of the feeding throat, powder is drawn and thickness reductionsfar in excess of those normally obtained may be accomplished. Obviouslythis structure may be employed in either a vertical or horizontal planeor configuration.

As noted above, the present process and apparatus, with very slightmodification, may be used for the continuous casting of metals and thelike. In this embodiment the preferred apparatus is disclosed in FIG. 3but for casting both the rolls (numbers 11 and 12 of FIGS. 1 and 2) arecooled and the two endless, flexible belts 21 and 22 are also cooled. Asnoted above as regards FIG. 3 the rolls are driven and the belts may bedriven or dragged by the rolls. Such belts are fully supported in thegrooves of the rolls. The two rolls and the two belts fully enclose anddefine a mold of rectangular cross section. All four walls of this moldmove together with the solidifying ingot at a rate selected for thematerial being cast. Friction is completely eliminated and separation ofthe ingot from the mold is automatically accomplished. Pouring rates areso adjusted that the porosity is eliminated in the converging section ofthe mold.

A modified form of the present invention is shown in FIG. 5, whereinparts similar to those shown in FIGS. 1 and 2 are indicated with thesame reference numeral and the subscript a. The apparatus includes a toproll 11a and a bottom roll 12a. The top roll has a central barrelportion 26 corresponding to the area between the grooves in FIG. 1 whichis of a noncircular configuration. In the embodiment shown the centralbarrel portion is provided with four recesses equally spaced around thecircumference. The resultant raised sections 29 and the recessedsections 28 correspond to the top surface of the shapes to be rolled. Inlike manner the bottom roll 12a also has a central barrel portion 27made up of similar recessed sections 30 and raised sections 31. In thisembodiment each of the recessed sections 28 and 30 and each of theraised sections 29 and 31 is geometrically symmetrical. The top roll 11aand the bottom roll 12a are rotated in opposite directions to cause theopposing faces to move the workpiece 13a in the same direction inconventional rolling fashion. The respective raised sections 29 and 31oppose each other as do the recessed sections 28 and 30 during therolling operation. This coordination is accomplished by conventionalmeans such as gears. The workpiece 13a which enters the rolls as a barof uniform cross section is transformed by the central barrel portionsof the rolls 11a and 12a into a periodic configuration of thick and thinsections in uniformly repeating patterns.

The lateral restraint is again accomplished by movable bars 16a. Theremainder of the apparatus is essentially the same as that shown inFIGS. 1 and 2. The flexible belts of FIG. 3 could again be substitutedfor the rigid bars shown in FIG. 5. The workpiece 13a is transformed byrolling from its initial cross sectional shape into the desiredconfiguration. The reduction is accomplished without edge cracking dueto the presence of the restraining bars 16a. Reductions in thickness upto 84% have been achieved without edge cracking or the formation offlash. The only limitation on use of the apparatus for periodic rollingis that the transitional surface of the rolls connecting the raisedsections and the recessed sections should not be undercut. Undercuttingof this transitional surface results in the pulling or tearing of theworkpiece as the roller attempts to free itself.

While the modification shown in FIG. 5 lends itself readily to the onestep rolling of any nonuniform shape the invention finds particularapplication in the field of rolling turbine blades.

Typical turbine blades formed by the process and apparatus of thisinvention are shown in FIGS. 6 and 7. FIG. 6 shows a continuous sectionof the workpiece after rolling and before cutting. The thick sectiondefines root portions 32 of two blades disposed end to end. The thinsection defines airfoil portions 33 of two blades disposed end to end.After cutting at the points indicated each turbine blade has the formshown in FIG. 7 or its mirror image. The airfoil portion 33 shown inFIG. 7 is laterally curved and tapered, however, it is not disposed atan angle to the root portion.

The airfoil cross section 33 shown in FIG. 7 is formed by one raisedsection 29 rolling in coordination with one raised section 31 in FIG. 5.For this particular application the raised section 29 of the upper roll11a is of a shape identical to the top boundary of airfoil 33. Matingraised section 31 is of a shape identical to the bottom boundary ofairfoil 33. The shape of the airfoil 33 and its angle to the rootsection 32 is 'Wholly a function of the shapes of the respective raisedand recessed sections of the central barrel portions of the rolls. If nomirror image blades are desired, the rolls can be designed to make onlyduplicate blades connected root to foil to root. Application of thepresent invention to the rolling of turbine blades will be more clearlyunderstood With reference to the following specific examples.

Turbine blades have been rolled with apparatus similar to that shown inFIG. 5. The width of the turbine blade and of the workpiece inserted inthree quarters of an inch. This width is maintained by spacing therestraining bars at three quarters of an inch and having the width ofthe central barrel portion of the top and bottom rolls also of threequarters of an inch width. Each turbine blade is 2% inches in totallength. The airfoil section is one and three quarters inches long andthe root section /2 inch long. The starting material is fed into theroll at a thickness of three fourths of an inch. The material is passedthrough the rollers in a single pass which produces turbine bladeshaving an airfoil thickness of 0.125 inch and a root thickness of 0.525inch. The raised portions of the rolls are correspondingly cut at athirty degree angle to the roll axis resulting in an airfoil portionwhich is also at a thirty degree angle to the sides of the root portion.Thematerials employed for this turbine blade configuration were 7075aluminum alloy rolled at 800 F. and Ti6Al -4 v. alloy rolled at 1800 F.

A larger turbine blade has been made from 7075 aluminum alloy rolled at800 F. The finished blade is one and fifteen-sixteenths inches wide and3.1 inches long. The airfoil section is 2.6 inches long. The rootthickness is .430 inch with the airfoil being again 0.125 inch. Thisairfoil is laterally curved and is rolled with no angle relative to theroot section.

It will be evident to one skilled in the art that many other complexshapes can be rolled without departing from the scope of this invention.Turbine blades have been employed merely by way of example. The centralbarrel portions of the rolls may be designed to yield one or severalrepetitions per revolution. One roll may be cylindrical and oneirregular in shape. The variations in geometry are almost unlimited.

The apparatus may be used for making preforms or for making end items.The tolerances of the roller parts depend on whether the product is tobe subjected to one final forging step or used as rolled. In either casethe process saves from 4 to 6 steps needed for current forming methods.

It will be understood that various modifications and variations may beaffected without departing from the spirit or scope of the novelconcepts of my invention.

I claim:

1. A method of rolling a series of periodic shapes from a workpiece ofrelatively constant cross section comprising the steps of:

feeding a workpiece between a pair of rolls each having a pair ofopposing circumferential grooves, at least one of said rolls having anoncircular cross section, and

restraining the sides of said workpiece from lateral movement by meansof a pair of relatively incompressible restraining bars received in saidgrooves and moving rectilinearly in the direction of the workpiecethroughout the rolling zone to limit lateral deformation of saidworkpiece during the rolling operation whereby the tensile forces alongthe lateral edges are sufficiently reduced to prevent edge crackmg.

2. Apparatus for rolling materials with complete lateral restraintcomprising:

a pair of rolls having spaced parallel rotational axes,

a pair of relatively incompressible elongate lateral restraining membersarranged to define a four sided enclosure in the plane common to saidaxes, said members being movable in the direction of rolling to limitlateral deformation of the workpiece during the rolling operationwhereby the tensile forces along the lateral edges are sufficientlyreduced to prevent edge cracking. 3. The apparatus defined in claim 2further comprising two pair of opposing grooves in said rolls, saidlateral restraining members being guided and supported in said grooves.

4. The apparatus defined in claim 2 wherein said lateral restrainingmembers are rigid bars.

5. The apparatus defined in claim 2 wherein said lateral restrainingmembers comprise endless incompressible belts of relatively flexiblematerial which receive their support from the walls of said grooves.

6. The apparatus defined in claim 2 wherein at least one of said rollsis of a noncircular profile with respect to its rotational axis.

7. An apparatus for rolling materials comprising a pair of spaced rollshaving parallel axes of rotation and defining a roll gap therebetween,each of said rolls including a pair of circumferential grooves inregister with the corresponding grooves on the opposite roll, and

a pair of lateral restraining members extending in the direction ofrolling and received in the respective opposing grooves on said rolls,said lateral restraining members being adapted for movement with thematerial to be rolled and further being relatively incompressible sothat they cooperate with said rolls and said grooves to provide completelateral restraint throughout the rolling pass whereby the tensile forcesalong said lateral edges are sufficiently reduced to prevent edgecracking. 8. A method as defined in claim 1 further comprising the stepof cutting the rolled shapes from the workpiece. 9. A method of rollingmaterials between at least one pair of rolls comprising the steps of:

feeding a workpiece between a pair of rolls each having a pair ofopposing circumferential grooves, and

restraining the sides of said workpiece from lateral movement throughoutthe rolling zone by means of a pair of relatively incompressiblerestraining bars received in said grooves and moving rectilinearly inthe direction of the workpiece whereby the tensile forces along thelateral edges are sufliciently reduced to prevent edge cracking.

References Cited UNITED STATES PATENTS 54,605 5/1866 Rogers 721923,222,907 12/1965 Polakowski 72250 3,415,095 12/1968 Bringewald 72-1922,932,852 4/1960 Melville et al 2641l1 FOREIGN PATENTS 837,198 4/1952Germany.

LOWELL A. LARSON, Primary Examiner US. Cl. X.R. 72190, 250

